The power to the output channels dont work but the front still lights up

There can be any number of reasons for this problem - solve it diagnostically by starting with something that you know is working and work through systematically to the other end.

1. Test a microphone on a separate amp to make sure it works okay. Check amp and speakers working. Check that all output cables from mixer to amp are working by testing separately.
2. Plug microphone into a channel on mixer. Also plug in headphones and turn headphone volume control up.
3. Make sure input sensitivity knob is turned up a bit (say half way) and main output faders (yellow) are up.
4. Check that channel is turned on (little button just above the channel fader- needs to be pressed down)
5. press pfl (pre-fade listen) button (next to button to switch channel on)- do you get any sound on main output or headphones or any indicator lights on mixer to show signal is getting that far (eitehr the individual channel metering lights or the main ones in the central section)?
6. turn off pfl - make sure channel fader (slider) is up - normal position is ) - about 3/4 of way up. Check lights again on individual channel and main output section - any signs?
7. Is the sub mix button for the channel pressed down - in which case you will need to bring sub mix (red) output faders up as well as main faders.
8. If you have got signs of signal on the individual channel but not main see if the channel has been routed somewhere odd (like a subgroup of channels).
9. Plug a working amp and speakers into one of the auxiliary outputs and use the relevant auxiliary send knob (on each channel just above the faders and pfl switches) to pan some signal to that auxiliary out - do you get anything? There is also a headphone socket for listening to the auxiliary channels (with a selector switch /knob to determine which one - make sure it is in the right position) try listening to the auxiliary output with headphones - anything? If yes the problem lies in the main output section.
10. Check that there is not a jack plug in the insert socket (to route signal through an external effects unit) without a matching return jack being plugged in - if appropriate is relevant effects unit switched on and correctly set up - if unsure remove the insert plug to take it out of the system.
11. Make sure any mute buttons are not switched in on main outputs.

You can download a full user manual here http://www.allen-heath.com/gl/gl2400

The left channel output in the amplifier stage is going out - could be a cold solder connection due to overheating. Check the left channel output of the power transistors solder trace - you can compare them to the right channel stage because they're almost identical circuits.

I am assuming you are using the standard sonamp 260 not a 260x3
and that when you say you are getting sound on only 1 pair that means only on 1 side (left or right channel only?)

Are using a speaker selector box? you must to regulate the resistance (ohms)

if so first unhook all but on pair of speakers and see if both channels are working.

if they do your problem is in the speaker selector not the amp if no then check to see what the amp level is set to. These are the two small holes on the front right of amp make sure they are set about equal at around half way up.

If that doesn't work flip the RCA cables coming to the amp perhaps you have a bad cable if that doesn't work make sure your receiver (source) is outputing a stereo signal to begin with.

lastly 8 sets of speakers off 1 amp? that's pushing it.even with a high quality Niles or speakercraft selector that controls the resistance going to an amp I wouldn't go past 5 sets.

The right way to do it would be to use 260x3 or a sonance or speakercraft 12 channel amp.

May be the problem is on the sound you are using is not a 5 channel coded sound or check in the menu´s of the amp if the rear channel´s have sufficient db output, check the connections, check if you amp. is not working only as simple stereo (menus also)

Hope this helps

Sounds like the power transistor(s) on that channel burned out. Needs service.

Sound to headphones comes from the pre-amp stage of most units otherwise they wouldnt be able to handle the power output . 150 watts into your ears ouch lol .
So it sounds like your slave amp has gone down on one channel . a slave amp is the final output stage and the power stage to the speakers . to make sure it is the amp change your speakers over if the sound then works from the speakers that had been dead then its the amp and requires an engineer to check it out with the prospect of a new output IC or final stage / capacitor replacement

unskilled persons should not attempt to repair electronic equipment as it is unsafe to do so , and may cost you far more in the long run ?. Regards Vortash

sounds like DC on that output.
needs service possibly fried all the output transistors on that channel

Grab yourself a test light and make sure that not only the 12v red power wire is putting out power but the thin blue or 12 volt turn on wire is also showing power. Then test the ground terminal and make sure u have a good ground. If that doesnt work try checking the amps fuses and check the fuse and connection on the battery. If everything checks out ok and the problem persists then put a small test speaker to the channel outputs and make sure that u are getting noise from those channels if you dont get any noise then u most likely have bad outputs and blown channels, you will need a new amp. Good luck, hope i was good help.

It sounds like you have a broken output filter inductor in the amplifier. You should be aware that the speaker outputs of the amp are biased at ~40v DC and can give a good shock if you touch the speaker wire while you're grounded (touching the body of the vehicle).

 

When you connected the speaker as you did, I would have expected the speaker to move in or out and remain there while the wire was connected to the housing of the amp. I'll assume that the amp was screwed down to the chassis of the vehicle. If it wasn't, you may have more than one problem.

This is not a problem that a normal comsumer should try to repair themselves. It's time to take it to a pro. It sounds like you have blown out at least one of your output channels. If you are getting any red light at all then the good news is that the power supply section of the amp is probably still good. About half of all the electronics in your amp is for the power supply section. The other half is for the actual amplifiers of the amp. Good luck, I hope it's not too bad.